Bendable catheter arms having varied flexibility

ABSTRACT

In various embodiments, a catheter comprising an expandable electrode assembly or basket is provided. In specific embodiments, the basket is particularly useful for mapping electrical activity at one or more locations within the heart. The basket can comprise a plurality of bendable or deflectable arms. At least one of the arms may have varied flexibility over its length in the form of one or more discontinuities of stiffness or flexibility at an elbow region or other variances in flexibility over the arm&#39;s length. Such variance in flexibility may allow the arm to assume a different bent configuration or respond to external factors more positively than possible with an arm having a static or near static flexibility or stiffness over its length.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application no.12/599,035, filed on Nov. 5, 2009 (the '035 application), now U.S. Pat.No. 8,224,416 issued on 17 Jul. 2012, which is the national stage ofinternational application no. PCT/US2008/063204, with an internationalfiling date of 9 May 2008 (the '204 application), which claims priorityto U.S. provisional application No. 60/917,053, filed on 9 May 2007 (the'053 application.). The '035 application, the '204 application, and the'053 application are each hereby incorporated by reference as thoughfully set forth herein.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention pertains generally to catheters and electrodeassemblies. More particularly, the present invention is directed towardmapping catheters including high density mapping catheters, and ablationcatheters.

b. Background Art

Electrophysiology catheters are used for an ever-growing number ofprocedures. For example, catheters are used for diagnostic, therapeutic,and ablative procedures, to name just a few examples. Typically, thecatheter is manipulated through the patient's vasculature and to theintended site, for example, a site within the patient's heart. Thecatheter typically carries one or more electrodes, which may be used forablation, diagnosis, or the like. There are a number of methods used forablation of desired areas, including for example, radiofrequency (RF)ablation. RF ablation is accomplished by transmission of radiofrequencyenergy to a desired target area through an electrode assembly to ablatetissue at the target site.

By mapping the electrical activities using mapping electrodes of acatheter, one can detect ectopic sites of electrical activation or otherelectrical activation pathways that contribute to cardiac disorders.This type of information is very valuable and allows a cardiologist tolocate and treat dysfunctional cardiac tissues. Ablation electrodes canbe provided on a catheter for ablating cardiac tissue. Ablation isconsidered a field within electrophysiology and is important because itobviates the need for more invasive and risky surgical treatments suchas open heart surgery.

Typically, the electrode catheter is inserted into a major vein orartery, and then guided into the heart chamber of concern. Due to theunpredictability of the interior size and shape of an individual's heartand the location of the area of concern, the ability to control theexact position and orientation of the catheter is essential and criticalto the effectiveness of the ablation treatment by electrode catheter.

Such electrophysiological ablation and mapping catheters typically havean elongated flexible body with a distal end that carries one or moreelectrodes that are used to map or collect electrical information aboutelectrical activities in the heart. Typically, the distal end issteerable to provide the user the ability to adequately guide andposition the catheter to the desired location. Some types of electrodeablation and mapping catheters (see, e.g., U.S. Pat. No. 7,027,851,which is hereby incorporated by reference in its entirety) use multipleelectrode arms or spines to allow multiple measurements to be taken atonce, thereby reducing the time it takes to map the heart. Although suchtypes of electrode ablation and mapping catheters make mapping moreefficient, they suffer from the lack of control over the individualelectrode spines or arms. In addition, because of the unpredictable andoften irregular shapes and sizes of the inner-heart, such uncontrollableindependent configuration of electrode spines or arms often lead tounreliable mapping and ablation, because the user cannot adequatelypredict or control where a particular electrode spine or arm will bepositioned relative to another electrode spine or arm. Accordingly, theneed exists for an improved catheter that can more effectively controland position multiple electrode members and increase locationpredictability of electrode members, while being steerable anddeflectable.

BRIEF SUMMARY OF THE INVENTION

In various embodiments, a catheter comprising an expandable electrodeassembly or basket is provided. In specific embodiments, the basket isparticularly useful for mapping electrical activity at one or morelocations within the heart. The basket can comprise a plurality ofbendable or deflectable arms. At least one of the arms can have variedflexibility over its length in the form of one or more discontinuitiesof stiffness or flexibility at an elbow region or other variances inflexibility over the arm's length. Such variance in flexibility canallow the arm to assume a different bent configuration or respond toexternal factors more positively than possible with an arm having astatic or near static flexibility or stiffness over its length.

Accordingly, in at least one embodiment, the catheter can comprise anelongated body having a proximal end and a distal end and an electrodeassembly at the distal end of the elongated body. In these embodiments,the electrode assembly can comprise a plurality of arms, each having aproximal end connected to the distal end of the elongated body and adistal end. Further, the distal ends of the arms can be connected at atip junction. Moreover, the electrode assembly is collapsible to acollapsed arrangement to fit within a lumen of a shaft and is alsoexpandable to an expanded arrangement. Additionally, at least one of thearms comprises at least one electrode and a support member. In theseembodiments, the support member can further comprise a distal portion, aproximal portion, and an intermediate portion therebetween. One of thedistal and proximal portions can define a first width and theintermediate portion can define a second width, where the first width isgreater than the second width. Accordingly, the flexibility of theintermediate portion can be enhanced or greater than the flexibility ofthe distal and/or proximal portions. Stated otherwise, the stiffness ofthe distal and/or proximal portions can be greater than the stiffness ofthe intermediate portion.

In various embodiments, an arm for an expandable catheter basket orelectrode assembly is provided. The arm can comprise a bendable supportmember defining a distal portion, a proximal portion, and anintermediate portion therebetween. The arm can further comprise meansfor enhancing flexibility of the intermediate portion relative to one orboth of the distal and proximal portions and at least one electrodepositioned along the support member. Such embodiments can provide an armthat is able to resist undesirable inversion when expanded or arched andin use.

In at least one embodiment, the means for enhancing flexibility can beprovided by the support member being narrower at the intermediateportion than the distal and/or proximal portions. Alternatively, in atleast one embodiment, the means for enhancing flexibility can beprovided by openings located in the intermediate portion. In otheralternate embodiments, the means for enhancing flexibility can beprovided by composite material layers and/or by varying the materialcomposition between the intermediate portion and the distal and/orproximal portions such that the flexibility of the intermediate portionis greater than the flexibility of the distal and/or proximal portions.

In various embodiments, an arm for an expandable catheter basket orelectrode assembly is provided. The arm can comprise a bendable supportmember defining a distal portion, a proximal portion, and anintermediate portion therebetween. The arm can further comprise meansfor enhancing flexibility of the distal and proximal portions relativeto the intermediate portion and at least one electrode positioned alongthe support member. Such embodiments can provide an arm that is able tobow, splay, or bulge outwardly more than otherwise possible at leastover the distal and/or proximal portions when expanded or arched,thereby favorably positioning the electrode(s), particularly anyelectrode(s) located at or near the distal or proximal portions of thesupport member.

In at least one embodiment, the means for enhancing flexibility can beprovided by the distal and proximal portions being tapered on one sideor on opposing sides of the support member. Alternatively, in at leastone embodiment, the means for enhancing flexibility can be provided byopenings located in the distal and/or proximal portions. In otheralternative embodiments, the means for enhancing flexibility can beprovided by composite material layers and/or by varying the materialcomposition between the intermediate portion and the distal and/orproximal portions such that the flexibility of the distal and/orproximal portions is greater than the flexibility of the intermediateportion.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a catheter system according to anembodiment of the present invention.

FIG. 2A is a perspective view of a catheter showing an electrodeassembly or basket in an expanded profile.

FIG. 2B is a perspective view of the electrode assembly in a collapsedprofile inside a sheath.

FIGS. 3A-3D illustrate the electrode assembly having spines formed ofgenerally linear spine segments at different stages of expansion fromthe collapsed profile to the expanded profile, and having electrodesdisposed between the elbows and the distal ends of the spines, accordingto an embodiment of the invention.

FIGS. 3E-3G illustrate an electrode assembly having arcuate shape spinesaccording to another embodiment of the invention.

FIGS. 4A-4D illustrate various configurations of internal supportmembers of spines according to different embodiments.

FIG. 5 is a perspective view of the tip junction of the electrodeassembly of a catheter according to an embodiment of the invention.

FIGS. 6A and 6B are side views of two catheter shafts showing differentdegrees of shaft deflection.

FIG. 7 is a side view of the distal region of a catheter shaft showingthe tilting of the electrode assembly using an adjusting member attachedto the tip junction.

FIG. 8 is a side view of a set of bendable support members of a basketcatheter in an expanded configuration, according to at least oneembodiment.

FIG. 9 is a side view of another set of bendable support members of abasket catheter in an expanded configuration, according to at least oneembodiment.

FIG. 10 is a side perspective view of one of the bendable supportmembers of FIG. 9.

FIG. 11 is a side perspective view of another bendable support member,according to at least one embodiment.

FIG. 12 is a side view of another bendable support member, according toat least one embodiment.

FIG. 13 is a side view of another bendable support member, according toat least one embodiment.

FIG. 14 is a side view of an arm of a basket catheter, according to atleast one embodiment.

FIG. 15 is a side view of an expanded catheter basket with at least onearm inverted.

FIG. 16A is a top view of a bendable support member, according to atleast one embodiment.

FIG. 16B is a cross-sectional view of a distal portion of the bendablesupport member of FIG. 16A, taken along line 16B-16B.

FIG. 16C is a cross-sectional view of an intermediate portion of thebendable support member of FIG. 16A, taken along line 16C-16C.

FIG. 16D is a cross-sectional view of a proximal portion of the bendablesupport member of FIG. 16D, taken along line 16D-16D.

FIG. 17 is a distal perspective view of a set of bendable supportmembers cut from a tube of material, according to at least oneembodiment.

FIG. 18 is a side view of a shape-set set of bendable support members,according to at least one embodiment.

FIG. 19 is a distal perspective view of the shape-set set of bendablesupport members of FIG. 18.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of ordinary skill in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the various embodiments of the present disclosure isdefined solely by the claims. The features illustrated or described inconnection with one exemplary embodiment may be combined with thefeatures of other embodiments. Such modifications and variations areintended to be included within the scope of the present disclosure.

FIG. 1 is a perspective view of a catheter system 1 according to anembodiment of the present invention. The catheter system 1 includes ahandle 2 and connectors 3 disposed proximal to the handle 2 for makingelectrical connections to an electronic mapping system or the like (notshown). The handle 2 can have a uni-directional design, a bi-directionaldesign, a double bi-directional design, or any other suitable design.The catheter system 1 also has a delivery sheath intro 4 located distalto the handle 2 that a surgeon may use to deliver a sheath 6 into thebody of a patient. The sheath 6 extends from the delivery sheath intro4. Further, an electrode assembly or basket 10 protrudes from the distalend of the sheath 6. As those of ordinary skill in the art willrecognize, the handle 2, the delivery sheath intro 4, and electronicconnectors 3 may readily be modified as dictated by the aesthetic orfunctional needs of particular applications.

FIGS. 2A and 2B illustrate the electrode assembly 10 in greater details.FIG. 2A shows the electrode assembly 10 in an expanded profile, whileFIG. 2B shows the electrode assembly 10 in a collapsed profile inside asheath 17. The electrode assembly 10 may be collapsed by a force to thecollapsed profile and, upon removal of the force, returns to theexpanded profile. This may be achieved by using a shape memory materialor some other biasing mechanism. The electrode assembly 10 shown haseight spines 11. Each of the spines 11 has a distal and a proximal end.The spines are deflectable elongated pieces that carry electrodes 12along a length of the spines 11. In this embodiment, a plurality ofelectrodes 12 are disposed between the elbow regions 20 (as discussedbelow in connection with FIGS. 3A-3D) and the distal ends of the spines11. When the electrode assembly 10 is in the expanded profile, accordingto this particular embodiment, the electrodes 12 on the spines 11 forman array of electrodes distributed over a substantially flat surfacewithin an area encircled by dashed line A. The electrode assembly 10 hasa generally cone shape in the expanded profile. Of course, the array ofelectrodes 12 need not be distributed over a substantially flat surfacebut may take on a nonplanar surface profile in the expanded state inother embodiments depending on the application of the electrodeassembly. In specific embodiments, the spines 11 include mappingelectrodes 12 that are spaced differently among the different spines 11so as to provide orientation information for the mapping. In otherembodiments, an ablation electrode is provided at one or more of theelbows 20 of the spines 11.

The distal ends of the spines 11 are connected at a tip junction 13 (seeFIG. 5). The electrode assembly 10 is coupled at its proximal end to adistal end of a longitudinal shaft 16, and the shaft 16 is slidablyreceived within a longitudinal lumen of the sheath 17. In FIG. 2B, thecollapsible electrode assembly 10 is in a collapsed profile and isslidably received within the longitudinal lumen of the sheath 17. Duringdelivery of the catheter into the target site within a patient's body,the electrode assembly 10 remains collapsed as shown in FIG. 2B. Theelectrode assembly 10 expands, as shown in FIG. 2A, when it is pushedthrough the distal end of the sheath 17 at the target site. The elbows20 of the spines 11 move radially outwardly and the spine tip junction13 move closer to the distal end of the catheter shaft 16 as theelectrode assembly 10 moves from the collapsed profile to the expandedprofile. The electrode assembly 10 is preferably biased from thecollapsed state toward the expanded state when the force applied to moveit to the collapsed state is removed. As discussed in more detail below,this can be achieved by using shape memory materials or the like.

The tip junction 13 may be a block with a plurality of transversethrough holes, as seen in FIG. 5. The transverse through holes receivespines 11. The spines 11 can be fastened to the tip junction 13 byadhesives, welding or other suitable means. The tip junction 13 isconnected to the distal end of an adjusting member 14 which may be inthe form of a control wire. The adjusting member 14 extends into theshaft 16 and is slidably received within the shaft. The proximal end ofthe adjusting member 14 is coupled to a user-actuated controller suchthat movement of the adjusting member 14 in a proximal direction willalso move the tip junction 13 in the proximal direction, which in turncauses the electrode assembly 10 to move toward or away from theexpanded profile as shown in FIG. 2A and FIG. 3A.

Optionally, the tip junction 13 can be an electrode for mapping and/orablating. In such an embodiment, the tip junction 13 is electricallyconnected to a power source and can selectively apply energy, or collectelectrical data, or both.

In the embodiment of FIG. 3A, the electrode assembly 10 has four spines11. The dashed lines illustrate different stages of collapse of theelectrode assembly 10 from the expanded profile by selectively andslidably move the adjusting member 14. In this embodiment, the proximalends of spines 11 are connected to a base socket support member 18 atthe distal end of the shaft 16. The base socket support member 18provides structural support to secure the plurality of spines 11 to theshaft 16, while allowing pivotal movement of individual spines 11 duringexpansion and during collapse of the electrode assembly 10.

As seen in FIG. 2A, a flat wire 15 is provided in the shaft 16 forbi-directional deflection of the shaft 16. In the embodiment shown, theflat wire 15 does not extend through the distal end of the shaft 16, andis contained within shaft 16. Additionally and optionally, shaftelectrodes 19 are disposed near the distal end of the shaft 16 forvisualization and/or mapping purposes as used, for instance, in theEnSite™ system available from St. Jude Medical.

FIGS. 3B-3D illustrate the electrode assembly 10 at different stages ofcollapse or expansion as the adjusting member 14 moves forward andbackward along the longitudinal direction of the shaft 16. The electrodeassembly 10 has spines 11 formed of generally linear spine segments.There are two spine segments separated by an elbow region 20 in anintermediate position between the distal end and the proximal end of theembodiment shown. A distal segment extends from the elbow 20 to thedistal end connected to the tip junction 13. A proximal segment extendsfrom the elbow 20 to the proximal end connected to the support member18. In this embodiment, electrodes are disposed between the elbows 20and the distal ends of the spines 11. The elbow 20 bends outwardlyrelative to the proximal end and the distal end of the spine 11. Theelbow 20 has at least one discontinuity in stiffness that allows it tobend. The at least one discontinuity may result from one or more of achange in material, a change in cross-sectional arrangement (e.g.,shape), and a change in cross-sectional area. In a specific embodiment,the cross section of the spine 11 changes from the proximal segment to aless stiff cross section at the elbow 20 (by reducing the area and/orthe shape of the cross section) and then changes back to the same crosssection in the distal segment as in the proximal segment. The elbow 20may be located in the mid portion of each spine 11. The location of theelbow 20 affects the size of the area A of the electrode array in thisembodiment (see circle A in dash line in FIG. 2A), and defines the shapeof the electrode assembly or basket 10. The elbow region 20 may beselected for each spine 11 to define a desired shape and size of area Afor the electrode array, for instance, based on the type and shape ofthe target tissue.

Other configurations of the electrode assembly or basket 10 arepossible. For example, FIGS. 3E-3G show spines 11 without elbow regions,and the spines 11 bend in an arcuate manner in response to movement ofthe adjusting member 14. As a result, a generally oval or sphericalshape is formed instead of a conical or diamond shape.

FIGS. 4A-4D illustrate various configurations of internal supportmembers of the spines 11 that define the deflection characteristics ofthe spines 11 according to different embodiments. In these embodiments,each spine 11 has an internal support member 21 embedded in a shelltypically having a circular cylindrical shape. The internal supportmember 21 provides structure integrity and defines elbow regions forspine deflection. Each support member 21 shown supports two opposingspines 11 that are joined at the tip junction 13. Referring to the fourdiamond-shaped internal support members 21 in FIGS. 4A-4D, the topmostpoint 22 of the diamond is where tip junction 13 is located. The twoterminal ends 23 of the internal support members are secured to basesocket support member 18. The distal segment 24 is disposed between theelbow region 25 and the topmost point 22, and the proximal segment 26 isdisposed between the elbow region 25 and the terminal ends 23. Thetopmost point 22 has a bent shape that can be achieved by adiscontinuity (similar to the elbow 25) or by use of a shape memorymaterial. An optional bent knee 29 is provided near each terminal end23. The elbows 25 are characterized by a change or discontinuity incross-sectional shape and area. Unlike a hinge, the elbow 25 in theseembodiments is typically not a point but a region that includes thediscontinuity in stiffness. In other embodiments, the elbow 25 willappear more like a point if the discontinuity is formed by a hinge orhinge-like mechanism.

More specifically, FIG. 4A shows an internal support member 21 that hasa flat, rectangular cross-sectional shape throughout. The proximalsegment 26 is wider than the distal segment 24 (and has a largercross-sectional area), and is thus structurally stronger againstdeflection. In some embodiments, the proximal segments 26 may besufficiently sturdy so that when the array of electrodes are pressedagainst tissues with ridges or irregularities on the surface of thetissue, the proximal segments 26 do not bend out of shape but supportand maintain the contact between the array of electrodes and the tissuesurface. Such a design maintains the integrity of the electrode assembly10 such that its shape is not changed when pressed upon ridges on thetissue surface.

In other embodiments, the distal segments 24 are relatively stiffer thanthe rest of the support member 21, so that at least when the electrodeassembly 10 is in an expanded profile, the distal segments 24 remainsubstantially straight. In yet other embodiments, the support member 21may have a generally uniform cross section except at the elbows 25 (andoptionally the topmost point 22) where the cross section is reduced insize or otherwise shaped to provide a discontinuity in stiffness orweaker area to facilitate deflection. As mentioned, a hinge mechanism orthe like may also be employed at the discontinuity.

In FIG. 4B, the internal support member 21 has a flat, rectangularcross-sectional shape in the distal segments 24 and in the elbow region25 only. The distal segments 24 and the elbow region 25 can be referredto as a tapered section 27, which is generally of a thinner and flatterprofile than proximal segments 26. The proximal segments 26 in FIG. 4Bhave a generally round cross-sectional shape, and are sized to bestructurally stiffer against bending than the elbow region 25.

In FIG. 4C, the internal support member 21 has a generally roundcross-sectional shape throughout. The proximal segments 26 are larger indiameter than the distal segments 24 and the elbow region 25.Alternatively, the entire internal support member can have a roundcross-sectional shape, except at the angled points (elbow region 25 andtopmost point 22) wherein a flat, rectangular cross-sectional shape orthe like is provided to enhance pivotal bending at those angle points.

In FIG. 4D, the internal support member 21 has a generally roundcross-sectional shape in the distal segments 24 and the elbow region 25.The proximal segments 26 have a generally flat, rectangularcross-sectional shape that is configured to be structurally stiffer thanthe distal segment 24 and the elbow region 25.

Although specific shapes of internal support member 21, spines 11, tipjunction 13, and base socket support member 18 are disclosed for thecollapsible electrode assembly 10, one of ordinary skill in the art willrecognize there are other ways to build a collapsible assembly. Forexample, instead of providing a unitary internal support member 21 thatpasses through a tip junction 13 to form opposing spines 11, one can usetwo opposing internal support members 21 for the two opposing spines 11that are connected at the tip junction 13 by welding or the like. Inaddition, the cross-sectional shapes and configuration of the internalsupport members 21 described may readily be modified as dictated by thefunctional needs of providing sufficient structure integrity, allowingdeflection in the elbow region 25 and other designated regions, andproviding sufficient stiffness in the distal segments 24 to ensure thatthe distal segments 24 remain substantially straight duringablation/mapping of tissue. Different thicknesses can also be utilizedin different areas along the support member 21 to achieve the desireddeflection. For example, the elbow region 25 and the topmost point 22can be thinner or otherwise made structurally more tenuous than otherparts of the support member 21, such that the desired bending occurs atthe elbow regions 25 and the topmost point 22, and not in other parts ofthe support member 21.

In specific embodiments, the spines 11 are generally evenly spaced inthe electrode assembly or basket 10 to form a stable and sturdystructure that allows the electrode array to maintain its shape duringuse. This is particularly helpful if the electrode array is adapted tocontact body tissue having ridges or an otherwise uneven surface (e.g.,cardiac tissue of the heart). One contemplated way of providingsufficiently sturdy spines 11 is to use flat internal support members 21that only bend bi-directionally. In this way, the electrode assembly 10can expand and collapse, but the spines 11 will not move from side toside. Another contemplated design is to have internal support members 21made of sufficiently stiff material such that side-to-side movement isminimized. Optionally, using a tip junction 13 that aligns each spine 11in position can help in ensuring that the array of electrodes are notaffected by ridges at the target tissue site.

In use, the internal support members 21 are embedded within shells ofthe spines 11. When the spines deflect between the collapsed andexpanded profiles, the elbow regions 25 bend while the distal segments24 and the proximal segments 26 remain substantially straight. Duringexpansion of the electrode assembly 10, the spines 11 form angularconfigurations as shown in FIGS. 3B and 3C to reach the expanded profileof FIG. 3D.

In addition to, or as an alternative to structural variations in theinner support member 21, the inner support member 21 may use materialvariation along the length of the support member 21 to cause the desireddeflection at the elbow regions 25. Furthermore, shape memory alloy suchas Nitinol may be used to facilitate bending at the elbow region 25 andmay also be adapted to bias the inner support member 21 toward theexpanded profile when the force that is applied to collapse theelectrode assembly 10 is removed.

Other embodiments that do not employ inner support members 21 embeddedwithin the spines 11 are expressly contemplated. In those embodiments,the spines 11 may be modified so that deflectability is a direct resultof the structural and/or material variation of the spines 11 themselves.In those embodiments, the spines 11 can have shapes and material make-upsimilar to those described above for the internal support members 21.For example, the spines 11 can have shapes similar to those of thesupport members 21 as depicted in FIGS. 4A-4D.

In yet another embodiment, the expansion and collapse of the electrodeassembly 10 can be controlled without using an adjusting member 14. Inone alternative design, no adjusting member is needed. Instead, theelectrode assembly 10 is biased toward the expanded profile when theforce that is applied to collapse the electrode assembly 10 is removed.This can be achieved, for instance, by using a shape memory materialsuch as Nitinol for the spines 11. In another alternative design, anadjusting member may be embedded in at least one of the spines 11 or apair of opposing spines 11 (in the same manner as the internal supportmember 21). The embedded adjusting member can be used to adjust theexpansion and collapse of the electrode assembly 10, while optionally ashape memory material or the like may be used to bias the electrodeassembly 10 toward the collapsed profile. Furthermore, the embeddedadjusting member may optionally be used to tilt the electrode assembly10 relative to the shaft 16.

While the electrode assembly 10 has been discussed in detail above, thefollowing relates to the directional control of the electrode assembly10 as effected by tilting movement of the electrode assembly 10 relativeto the shaft 16 as well as tilting of the shaft 16. As shown in FIG. 2A,the flat wire 15 is disposed within the shaft 16 for bi-directionaldeflection of the shaft 16. One of ordinary skill in the art willrecognize that other types and shapes of wires can be used in place of,or in addition to, the flat wire 15 to effectuate the sameunidirectional, bidirectional or multi-directional deflection. FIGS. 6Aand 6B are side views of two catheter shafts showing different degreesof shaft deflection. FIG. 6A shows a larger degree of deflection thanFIG. 6B.

In yet another embodiment, the adjusting member 14 can optionally bedeflectable, much like the flat wire 15, or with the help of anadditional flat wire (not shown) or guide wire (not shown). Referring toFIG. 7, by making the adjusting member 14 user-selectively deflectable,a user can tilt the electrode assembly 10 and control the degree anddirection of the tilt by deflecting the adjusting member 14. In thatcase, the adjusting member 14 may be formed as a flat wire.

In still another embodiment, the flat wire 15 within the shaft 16controls tilting of the shaft 16, while a deflectable adjusting member14 controls tilting of the electrode assembly 10 relative to the shaft16. This can be referred to as a dual distal deflection design, allowingthe user to separately tilt the electrode assembly 10 (as shown in FIG.7) and also tilt the shaft 16 in another direction (as shown in FIGS. 6Aand 6B). This combination provides enhanced maneuverability anddexterity of the electrode assembly 10 of the basket catheter.

In various embodiments, the spines or arms of an expandable catheterbasket may have different configurations than those discussed above. Forexample, referring to FIG. 8, a catheter may generally comprise a basket110 including a plurality of arms, where each arm comprises a bendablesupport member 121 defining a distal portion 124, a proximal portion126, and an intermediate portion 125 therebetween. The bendable supportmembers 121 may comprise any number of elastic materials, such as metalsand/or plastics, for example. In various embodiments, the supportmembers 121 may be formed from superelastic or shape memory material,such as Nitinol, and/or a polymer, such as polyimide. When expanded, asshown, the basket 110 may define an expanded shape for supporting one ormore electrodes that can be used in contact and/or non-contact mappingof intracardiac potentials, for example. More detail on such mapping canbe found in U.S. Pat. No. 7,831,288, titled METHOD FOR MAPPING POTENTIALDISTRIBUTION OF A HEART CHAMBER, hereby incorporated by reference asthough fully set forth herein.

Referring now to FIG. 9, the shape formed by an expanded basket, such asbasket 110 ^(X), may be varied from that shown in FIG. 8. For example,the bendable support members 121 ^(X) of FIG. 9 may splay or bowoutwards further near their ends and/or more uniformly from the basket'slongitudinal axis L_(B) than that shown in FIG. 8 due to variance in theflexibility or stiffness of the arm 121 ^(X) over its length. In otherwords, while the support members 121 shown in FIG. 8 may have arelatively constant measure of flexibility over each one's length, thedistal portion 124 ^(X) and/or the proximal portion 126 ^(X) of at leastone of the bendable support members 121 ^(X) shown in FIG. 9 may have anenhanced or increased measure of flexibility compared to the flexibilityof the intermediate portion 125 ^(X) such that the distal and/orintermediate portions 124 ^(X), 126 ^(X) of the support member 121 ^(X)(FIG. 9) bend outwardly further than those of a comparable supportmember 121 (FIG. 8). In at least one embodiment, the support members 121^(X) may be similar or nearly identical to one another in terms of theirlongitudinal flexibility to provide a basket 110 ^(X) having an expandedshape that is symmetric about its longitudinal axis as shown in FIG. 9,for example.

Referring now to FIG. 10, a bendable support member 121 ^(I) may be seenin more detail in its straight, unbent form. In addition to thatdescribed above, support member 121 ^(I) may comprise an elongated bodydefining distal end 128 ^(I), proximal end 123 ^(I), and longitudinalaxis L. The flexibility of the distal and/or proximal portions 124 ^(I),126 ^(I) may be enhanced relative to the intermediate portion 125 ^(I)due to the distal and proximal portions 124 ^(I), 126 ^(I) being taperedor sloped on a first side, such as top side 131 ^(I), of the supportmember 121 ^(I). Notably, a second side opposing the first side, that isbottom side 132 ^(I), may be straight and untapered. The distal portion124 ^(I) and/or proximal portion 126 ^(I) may be tapered or sloped fromthe thicker intermediate portion 125 ^(I) towards the thinner portion ofthe support member at the ends 128 ^(I) or 123 ^(I) over the distal orproximal portions 124 ^(I), 126 ^(I), respectively. Additionally, such atapering of the distal portion 124 ^(I) and/or proximal portion 126 ^(I)may provide a gradual slope to minimize stress risers when the supportmember's ends 128 ^(I), 123 ^(I) are compressed towards one another suchthat the intermediate portion 125 ^(I) deflects outward, in thedirection of arrow D, for example.

Alternatively and although not shown, the flexibility of the distal andproximal portions of a bendable support member may be enhanced relativeto the intermediate portion by adding a stiffener layer, such aspolyimide, for example, to form the intermediate portion. A base layerof the support member, to which the stiffener layer may be added, mayalso be polyimide, for example. Thus, a bendable support member may havea varying thickness created from the same material, where the thickerportion is created by adding a stiffener layer of the same material as abase layer. In such an embodiment, the distal and/or proximal portionmay have a length of approximately 0.7670 inches and the intermediateportion, over which a stiffener may be added, may have a length ofapproximately 0.8000 inches, with a total support member length ofapproximately 2.3 to approximately 2.4 inches. In at least oneembodiment, the total support member length may be approximately 2inches.

While only one side of the support member 121 ^(I) may be tapered, otherembodiments are contemplated. For example, a bendable support member,such as support member 121 ^(II) illustrated in FIG. 11, may includedistal and proximal portions 124 ^(II) and 126 ^(II) that may be taperedon their opposing sides 131 ^(II) and 132 ^(II), respectively, therebyproviding a support member with additional flexibility over suchportions. The support member 121 ^(II) may be generally similar tosupport member 121 ^(I) described above in that it also includes distaland proximal ends 128 ^(II) and 123 ^(II), respectively, and isconfigured such that during expansion, the intermediate portion 125^(II) deflects outwards, generally in the direction of arrow D when thesupport member's ends 128 ^(II), 123 ^(II) are compressed towards oneanother.

In addition to varying the thickness of a support member over its lengthto affect the shape of the support member when expanded or deflected,other embodiments are contemplated. For example, a bendable supportmember, such as support member 121 ^(III) illustrated in FIG. 12, mayinclude slots or openings 130 ^(III) in the distal and/or proximalportions 124 ^(III) and 126 ^(III), respectively. The lack of materialin the openings 130 ^(III) allows the support member 121 ^(III) to bemore flexible in the distal and proximal portions 124 ^(III), 126 ^(III)than in the intermediate portion 125 ^(III). The support member 121^(III) may be generally similar to support member 121 ^(I) describedabove in that it also includes distal and proximal ends 128 ^(III) and123 ^(III), respectively, and is configured such that during expansion,the intermediate portion 125 ^(III) deflects outwards, generally in thedirection of arrow D when the support member's ends 128 ^(III), 123^(III) are compressed towards one another.

In another exemplary embodiment, a support member, such as supportmember 121 ^(IV) illustrated in FIG. 13, may include composite materialsin the distal and/or proximal portions 124 ^(IV) and 126 ^(IV),respectively, which provide increased flexibility in such portionsrelative to the intermediate portion 125 ^(IV) therebetween. In such anembodiment, the distal and proximal portions 124 ^(IV), 126 ^(IV) mayeach comprise an outer or first layer of material 130 ^(IV) and an inneror second layer of material 133 ^(IV). The first layer 130 ^(IV) maycomprise a first material, such as polyimide or other polymer, and thesecond layer 133 ^(IV) may comprise a second, different material, suchas Nitinol, Nitinol wire, metallic braids, and/or a material having adifferent durometer than the first material, for example. Additionally,the second layer 133 ^(IV) may have a shape similar to the supportmember 121 ^(II) seen in FIG. 11 and discussed above. Thus, the secondlayer 133 ^(IV) may form the majority of the material composition of theintermediate portion 125 ^(IV), whereas the distal and proximal portions124 ^(IV), 126 ^(IV) may comprise a material composition comprised moreof the first material than the second material. The first material maybe more flexible than the second material and therefore provide enhancedflexibility to the distal and/or proximal portions 124 ^(IV) and 126^(IV) respectively. Additionally, owing to the layers of materials, thesupport member 121 ^(IV) may have a consistent thickness and/or widthalong its length even though the flexibility of the support member 121^(IV) is varying over the support member's length.

As mentioned above, one or more arms of an expandable catheter basketmay comprise at least one electrode through which a support member maypass. In various embodiments, each arm may comprise multiple electrodesspaced along the entire length of the arm. For example, in at least oneembodiment, a first electrode may be positioned at or over a segment ofthe distal portion of the arm's support member, a second electrode maybe positioned at or over a segment of the intermediate portion of thearm's support member, and a third electrode may be positioned at or overa segment of the proximal portion of the arm's support member.Additionally, a support member may be inserted through the electrodessuch that there are multiple electrodes at one or more of the distal,intermediate, and proximal portions. The electrodes along an arm oralong each of the arms may be the same or different in size. In at leastone embodiment, the electrodes along each arm may be the same size,which may enhance the non-contact mapping capabilities of an expandablecatheter basket.

For example, referring to FIG. 14, a basket arm 111 is shown with abendable support member 121 inserted through a shell or jacket 134including electrodes 112. Wires connected to the electrodes have beenomitted for clarity. The jacket may comprise a flexible polymer, such asa polyether block amide (“PEBA”) or similar plastic material, forexample. Support member 121 shown in FIG. 14 may be any of the supportmembers described herein, such those shown in FIGS. 10-13 (describedabove) or FIG. 16A (described below), for example. As can beappreciated, the shape of the support member 121 when expanded ordeflected will cause the jacket 134 and the electrodes 112 positionedalong the support member 121 to similarly deflect into an expandedconfiguration. Accordingly, by varying the shape of the support memberwhen in an expanded configuration as discussed above, the spacing ofelectrodes 112 from electrodes on other arms of the expandable catheterbasket may be optimized.

While the variance of arm and/or support member flexibility may allowfor differing expanded basket shapes, such variance may also be utilizedto further enhance a catheter's performance during a surgical procedure.For example, referring to FIG. 15, an expandable catheter basket 10 andrelated components are shown. The catheter basket 10 may be similar tothat shown in FIG. 3E and described above in that an adjusting member 14is shown having pulled a tip junction 13 toward a shaft 16 to cause thecatheter basket 10 and arms 11 to attempt to deflect into an expandedconfiguration. However, while the catheter basket 10 may generally be inan expanded configuration, at least one of the arms, such as arm 11′, isshown in an inverted state. This inverted state may occur during aprocedure such that the arm 11′ splays inward, toward and/or past thelongitudinal axis L_(B) of the shaft 16, control wire 14, and/or tipjunction 13. In at least one embodiment, the inversion of a basket'sarms may be minimized by configuring the arms to resist inversion,thereby helping keep the electrodes 12 spaced apart from one another ata desired distance during a surgical procedure. In at least oneembodiment, an arm may be so configured by providing a support memberwith enhanced flexibility near its middle region as compared to its endregions.

Referring now to FIG. 16A, a top view of a bendable support member 221of an arm of a catheter basket is shown. The support member 221, whenassembled in a catheter basket, may be configured to deflect in or outof the plane of the page of FIG. 16A, in other words, towards or awayfrom the viewer. The support member 221 may comprise a distal portion224, a proximal portion 226, and an intermediate portion 225therebetween and define a longitudinal axis L. Further, in at least oneembodiment, the width of the support member 221 may vary along itslength such that it is narrower or thinner near or about its middleregion.

In more detail, FIGS. 16B, 16C, and 16D illustrate cross-sections of thesupport member 221 taken along lines 16B-16B, 16C-16C, and 16D-16D,respectively, where each line defines a plane transverse to thelongitudinal axis L (see FIG. 16A). In these figures, cross-hatching hasbeen omitted for the purposes of clarity. As can be seen, the distalportion 224 may define a rectangular, first cross-sectional shape havinga first width w₁ and a first height h₁ (FIG. 16B), the intermediateportion 225 may define a rectangular, second cross-sectional shapehaving a second width w₂ and a second height h₂ (FIG. 16C), and theproximal portion 226 may define a rectangular, third cross-sectionalshape having a third width w₃ and a third height h₃ (FIG. 16D). Theheight of the support member may be relatively uniform, thus, the first,second, and third heights h₁, h₂, and h₃ may be approximately equivalentto each other. However, the first and third widths w₁ and w₃,respectively, may each be greater than the second width w₂.Additionally, the first and third widths w₁ and w₃ may be approximatelyequivalent to each other when measured at similar distances from thedistal and proximal ends, 228 and 223, respectively, of support member221. Accordingly, the first and third cross-sectional shapes (FIG. 16B)may each define a contiguous area that is greater than the area definedby the second cross-sectional shape and the area of the first and thirdcross-sectional shapes may be approximately the same.

In terms of overall shape of the support member 221, at least theintermediate portion 225 may be curved inward on at least one side ofthe intermediate portion 225 to minimize stress risers and the like. Asshown, the distal, intermediate, and proximal portions 224, 225, and226, respectively, are curved inward on two opposing sides 241 and 242to form an hourglass-like shape. Further, the sidewalls on both sides241 and 242 may define parabolic profiles over the intermediate portion225 and/or the distal and proximal portions 224, 226 when viewed from atop (or bottom) view as shown in FIG. 16A. In at least one embodiment,the narrowest width of the support member 221, when viewed from the top,occurs at the midpoint of the support member 221. For clarity, the planedefined by line 16C-16C in FIG. 16A occurs at the midpoint of thesupport member 221, that is, halfway between the ends 228 and 223. Morespecifically, in at least one embodiment, the minimum or second width w₂is approximately 0.007 inches, and the first and third widths w₁ and w₃,when measured at or near the distal and proximal ends 228 and 223,respectively, are each approximately 0.013 inches. Also, the length ofthe support member 221, from the distal end 228 to the proximal end 223,is approximately 2 inches.

The variance in cross-sectional shape along the length of the bendablesupport member 221 leads to the intermediate portion 225 having anenhanced flexibility as compared to each of the distal and proximalsections 224 and 226. The increased flexibility at the intermediateportion 225 is at least partly due to the decrease in cross-sectionalarea, and, hence, the amount of material available to resist bending,over the intermediate portion 225 relative to the distal and proximalportions 224 and 226. In other words, the bendable support member 221may be narrower at or near its middle than at or near its ends 228 and223.

In more detail, referring to FIG. 16C, the intermediate portion 225 maybe configured to deflect in the direction of arrow D when the supportmember 221 is bent with the ends 228 and 223 (see FIG. 16A) movingcloser to each other. The flexibility of a beam at a plane, such assupport member 221 seen in FIGS. 16B-16D, is inversely related to itscross-sectional shape's second moment of area at those planes; stateddifferently: the less the second moment of area, the greater theflexibility. In bending situations such as those being presentlydiscussed, the second moment of area of the intermediate portion 225about the y-axis (passing through the shape's centroid or longitudinalaxis L in FIG. 16C), I_(y2), may be calculated approximately as follows:

$I_{y\; 2} = \frac{w_{2}h_{2}^{3}}{12}$Similarly, the second moments of area of the distal and proximalsections 224 and 226 about the y-axes (seen in FIGS. 16B and 16D),I_(y1) and I_(y3), respectively, may be calculated approximately asfollows:

$I_{y\; 1} = \frac{w_{1}h_{1}^{3}}{12}$$I_{y\; 3} = \frac{w_{3}h_{3}^{3}}{12}$As noted above, the second width w₂ is less than either of the first orthird widths w₁ and w₃ and the first, second, or third heights, h₁, h₂,and h₃, are approximately the same. Accordingly, in at least oneembodiment, the second moment of area of the intermediate portion 225about the y-axis, I_(y2), is less than the corresponding second momentsof area of the distal or proximal portions 224 and 226, I_(y1) andI_(y3). Subsequently, the flexibility of the intermediate portion 225 islikewise greater than that of the distal or proximal portions, 224 and226.

When the support member 221 is in a desired expanded or archedconfiguration (see FIG. 9, for example), the enhanced flexibility of theintermediate portion 225 relative to the distal and proximal portions224 and 226 may allow the distal and proximal portions 224 and 226 toresist inversion while the intermediate portion 225 may not contributemuch resistance, mechanically speaking, to holding support member 221 orcausing the support member 221 to reside in an inverted state. Moreover,if a support member 221 did invert during use, the support member 221may be more likely to reverse such inversion and return to the desiredexpanded or arched configuration owing to the enhanced flexibility atthe intermediate portion 225. In other words, the intermediate portion'senhanced flexibility may allow for the inversion of any support members221 to only be a temporary event.

Referring now to FIG. 17, in addition to methods described above forcreating the support members of an expandable catheter basket, thesupport members of a basket, such as basket 210, may be formed asfollows. In at least one embodiment, a tube, such as a Nitinol hypotube,may be cut or formed to provide support members 221. In variousembodiments, a Nitinol hypotube may have an outer diameter ofapproximately 0.098 inches, approximately 0.097 inches, or approximately0.060 inches. Additionally, in various embodiments, the inner diametermay be approximately 0.089 inches (for tubes having an outer diameter ofabout 0.098 or about 0.097 inches) or approximately 0.050 inches (fortubes having an outer diameter of about 0.060 inches). As mentionedabove, the length of a support member 221 may be about 2 inches,accordingly as illustrated in FIG. 17, a hypotube may be over 2 inchesin length.

In at least one embodiment, the Nitinol hypotube may be laser cut toremove material, resulting in basket 210 seen in FIG. 17. The basket 210may comprise support members 221 between a distal end ring 251 and aproximal end ring 252 and may define a longitudinal axis L_(B). Asdiscussed above, each support member 221 may comprise a distal portion224, a proximal portion 226, and an intermediate portion 225therebetween. Opposing sides 241, 242 of the support member 221 may betapered or curved inward, resulting in the intermediate portion 225being narrower than the distal or proximal portions 224, 226 as measuredin a circumferential direction of the basket 210. The distal andproximal ends 228 and 223 (highlighted with dotted lines in FIG. 17) ofthe support members 221 may be integrally connected to the distal andproximal end rings 251 and 252, respectively. Further, the proximal end223 of a support member 221 may be integrally coupled to the proximalend ring 252 by proximal extension 253. Although not shown, the proximalextensions 253 may be further cut transversely to remove the proximalend ring 252 from the basket 210 and provide a free end to supportmember 221 such that one or more electrodes and/or a polymer jacket maybe slid thereover (see, e.g., FIG. 14). Afterwards, the support members221 and/or extensions 253 may be coupled to a catheter shaft, such asshaft 16 discussed above, and the distal end ring 251 may form at leasta portion of the catheter's tip, such as tip junction 13 also discussedabove (see, e.g., FIGS. 3E and 15).

Referring now to FIGS. 18 and 19, in at least one embodiment, supportmembers, such as Nitinol support members 321 extending from distal endring 351, may be biased outwards, away from the longitudinal axis L_(B)of an expandable basket 310. To achieve such a biasing, a mandreldefining the biased shape seen in FIGS. 18 and 19 may be first insertedinto the lumen defined between the support members 321, therebyelastically deflecting them towards the illustrated shape. Then, thebasket 310 and mandrel may be placed into an oven and heated such thatthe Nitinol support members become at least partially malleable.Immediately thereafter, the basket 310 and mandrel may be placed in acooling bath of water, thereby resulting in the support members 321becoming heat set into the shape as shown in FIGS. 18 and 19.Accordingly, the shape-set support members 321 may be in an at leastpartially retracted state as shown in FIGS. 18 and 19 but may already bebiased at least partially outward, away from the longitudinal axis L_(B)to help ensure that the desired shape of the support members is achievedwhen fully expanded as discussed above, that is by moving the distal endring 351 in a proximal direction.

While the foregoing has discussed the geometric narrowing of a supportmember to provide enhanced flexibility of the member's intermediateportion relative to its distal and/or proximal portions, it iscontemplated that one or more other flexibility enhancements may beutilized in an intermediate portion of a support member. For example,slots or openings, such as openings 130 ^(III) shown in FIG. 12 anddiscussed above, may be added to a support member's intermediate portionin place of or in addition to the geometric narrowing of theintermediate portion. Likewise, stiffeners or composite material layers,such as layers 130 ^(IV) and 133 ^(IV) seen in FIG. 13 and discussedabove, may be added to a support member to vary the material makeup ofthe support member over its length and provide enhanced flexibility ofthe member's intermediate portion relative to its distal and proximalportions. As noted above, varying materials over the length of eachsupport member may also include using different durometer materials,selectively applying Nitinol and/or Nitinol wire, incorporating metallicbraids, etcetera.

Although a number of representative embodiments according to the presentteachings have been described above with a certain degree ofparticularity, those skilled in the art could make numerous alterationsto the disclosed embodiments without departing from the scope of thisinvention. For example, while the bendable support members may beintegrally formed from a tube, it is contemplated that the supportmembers may be independently formed and then coupled using additionalcomponents. All directional references (e.g., upper, lower, upward,downward, left, right, leftward, rightward, top, bottom, above, below,vertical, horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure may be made without departing from theinvention as defined in the appended claims.

What is claimed is:
 1. A catheter, the catheter comprising: an elongatedbody having a proximal end and a distal end; and an electrode assemblyat the distal end of the elongated body, the electrode assemblycomprising a plurality of arms, each of the arms having a proximal endconnected to the distal end of the elongated body and a distal end, thedistal ends of the arms being connected at a tip junction, wherein theelectrode assembly is collapsible to a collapsed arrangement to fitwithin a lumen of a shaft and is expandable to an expanded arrangement;wherein at least one arm of the plurality of arms comprises: a shell; atleast one electrode; and a support member disposed within the shell, thesupport member comprising a distal portion, a proximal portion, and anintermediate portion therebetween, wherein one of the distal andproximal portions define a first width and the intermediate portiondefines a second width, and wherein the first width is greater than thesecond width.
 2. The catheter of claim 1, wherein the intermediateportion is curved inward on at least one side of the intermediateportion.
 3. The catheter of claim 2, wherein the support membercomprises a sidewall having a parabolic profile over the intermediateportion.
 4. The catheter of claim 2, wherein the intermediate portion iscurved inward on opposing sides of the intermediate portion.
 5. Thecatheter of claim 4, wherein the distal portion defines the first widthand the proximal portion defines a third width, and wherein the thirdwidth is greater than the second width.
 6. The catheter of claim 5,wherein the at least one electrode comprises multiple electrodes.
 7. Thecatheter of claim 6, wherein the multiple electrodes comprise a firstelectrode positioned at the distal portion, a second electrodepositioned at the intermediate position, and a third electrodepositioned at the proximal portion.
 8. The catheter of claim 7, whereineach electrode is approximately the same size.
 9. A catheter comprising:an expandable catheter basket comprising a plurality of arms, wherein atleast one of the arms comprises: a shell; a bendable support memberdisposed within the shell, the support member defining a distal portion,a proximal portion, and an intermediate portion therebetween; means forenhancing flexibility of the intermediate portion relative to one of thedistal and proximal portions; and at least one electrode positionedalong the support member.
 10. The arm of claim 9, further comprisingmeans for enhancing flexibility of the intermediate portion relative toboth of the distal and proximal portions.
 11. The arm of claim 9,wherein the means for enhancing flexibility of the intermediate portionrelative to one of the distal and proximal portions comprises the distalor proximal portion defining a first cross-sectional shape at a firstplane transverse to a longitudinal axis of the bendable support memberand the intermediate section defining a second cross-sectional shape ata second plane transverse to the longitudinal axis, wherein the firstcross-sectional shape has a second moment of area that is greater than asecond moment area of the second cross-sectional shape.
 12. The arm ofclaim 11, wherein the first cross-sectional shape defines an area thatis greater than an area defined by the second cross-sectional shape. 13.The arm of claim 11, wherein the first cross-sectional shape is widerthan the second cross-sectional shape.
 14. The arm of claim 13, whereinthe distal portion defines the first cross-sectional shape and theproximal portion defines a third cross-sectional shape at a third planetransverse to the longitudinal axis, and wherein the thirdcross-sectional shape has approximately the same width as the firstcross-sectional shape.
 15. The arm of claim 9, wherein the means forenhancing flexibility of the intermediate portion relative to one of thedistal and proximal portions comprises the intermediate portion beingcurved inward on at least one side of the intermediate portion.
 16. Thearm of claim 15, wherein the intermediate portion is curved inward onopposing sides of the intermediate portion.
 17. The arm of claim 9,wherein the means for enhancing flexibility of the intermediate portionrelative to one of the distal and proximal portions comprises openingslocated in the intermediate portion.
 18. The arm of claim 9, wherein themeans for enhancing flexibility of the intermediate portion relative toone of the distal and proximal portions comprises the intermediate layercomprising a first layer and a second layer, wherein the first layercomprises a first material and the second layer comprises a secondmaterial, and wherein the first material is different from the secondmaterial.
 19. The arm of claim 9, wherein the means for enhancingflexibility of the intermediate portion relative to one of the distaland proximal portions comprises the distal or proximal portioncomprising a first material and the intermediate portion comprising asecond material, wherein the first material is different from the secondmaterial.
 20. A catheter, the catheter comprising: an elongated bodyhaving a proximal end and a distal end; and an electrode assembly at thedistal end of the elongated body, the electrode assembly comprising aplurality of arms, each of the arms having a proximal end and a distalend; wherein at least one arm of the plurality of arms comprises: ashell; at least one electrode; and a support member disposed within theshell, the support member comprising a distal portion, a proximalportion, and an intermediate portion therebetween, wherein one of thedistal and proximal portions define a first width and the intermediateportion defines a second width, and wherein the first width is greaterthan the second width.